ASTM D471 Standard Test Method for Rubber Property - Effect of Liquids
18. Report
18.1 State that the test was conducted in accordance with Test Method D471 and report the following:
18.1.1 Description of the sample and its origin,
18.1.2 Date and temperature of testing room (see 5.1),
18.1.3 Duration, temperature, and date of vulcanization of test specimens,
18.1.4 Dates of the various periods of exposure,
18.1.5 Immersion liquid used,
18.1.6 Temperature of exposure,
18.1.7 Exposure period,
18.1.8 All observed and recorded data, to include the type of properties being reported,
18.1.9 Results calculated in accordance with Section 17,
18.1.10 Statement of condition of exposed specimens from visual and manual examination,
18.1.11 Report which test method was used for determination of hardness, and
18.1.12 Any deviations from standard test methods.
19. Precision and Bias
19.1 This precision and bias section deals with property changes in tensile strength, ultimate elongation, hardness, and volume after immersion in test liquids and has been prepared in accordance with Practice D4483. Refer to this practice for terminology and other statistical calculation details.
19.2 The precision results in this precision and bias section give an estimate of the precision of this test method with the materials used in the particular interlaboratory test program as described in the following paragraphs. The precision parameters should not be used for acceptance or rejection testing of any group of materials without documentation that the parameters are applicable to the particular group of materials and the specific testing protocols of the test method.
19.3 A Type 1 interlaboratory test program was evaluated in 1981 using six different vulcanized rubber compounds (materials). These compounds were prepared in one laboratory and test specimens were distributed to nine participating laboratories. Each laboratory prepared and purchased from approved sources, the liquids and fuels, or both, used for testing. A test result (as used for these calculations) is the average of three individual test specimen values. Each laboratory conducted tests (that is, obtained one test result) on each of two days. Both repeatability and reproducibility are therefore short term; a period of a few days separates test results.
19.4 The results of the precision evaluation are given in Table 5 and Table 6 for each of the six rubbers or materials for immersion tests in (1) Reference Fuels B, C and D, for 70 h at 23 +/- 2°C (73 +/- 4°F), and (2) ASTM Oil No. 2 and ASTM Oil No. 3 for 70 h at 150 +/- 2°C (302 +/- 4°F).
19.5 The precision is given in terms of Sr, r, SR, and R for four measured physical properties: (1) percent change in tensile strength, (2) percent change in ultimate elongation (that is, percent change in percent elongation), (3) hardness change in hardness units, and (4) percent change in volume of the test specimen. No values are given for (r) and (R), the normal precision parameters used to express relative precision because numerous average values for properties (1), (2), and (4) are near zero, thus resulting in extremely large (r) and (R) values. These large values are essentially meaningless for precision comparisons when average values are near zero.
19.6 The precision of the test method may be expressed in the following statements that use an appropriate value of r and R. The appropriate value is that value of r or R, associated with a mean level in the tables closest to the mean level under consideration for any immersion liquid or rubber, for any test result for a similar material in routine testing operations.
19.7 Repeatability - The repeatability, r, of this test method has been established as the appropriate value tabulated in Table 5 and Table 6. Two single test results, obtained under normal test method procedures, that differ by more than this tabulated r (for any given level) must be considered as derived from different or nonidentical sample populations.
19.8 Reproducibility - The reproducibility, R, of this test method has been established as the appropriate value tabulated in Table 4 through Table 6. Two single test results obtained in two different laboratories, under normal test method procedures, that differ by more than the tabulated R (for any given value) must be considered to have come from different or nonidentical sample populations.
19.9 Bias - In test terminology, bias is the difference between an average test value and the reference (or true) value. Reference values do not exist for this test method since the value (of the test property) is exclusively defined by the test method. Bias, therefore, cannot be determined.
20. Keywords
20.1 elevated temperature; fluid immersion; liquid immersion; reference fuel; rubber articles; rubber products; service liquid
